This invention relates to papermaker's fabrics and more particularly to an anti-contaminant treatment for papermaking fabrics and that imparts anti-sticking characteristics to the fabric so that contaminants are easily removed.
Papermaking fabrics for use in papermaking machines usually are in the form of a fine mesh cloth which has been woven endless or otherwise joined into an endless web.
At one time, all papermaking fabrics were manufactured from metal wires. These metal-wire cloths were useful in all kinds papermaking machines and for all paper qualities. Eventually, metal wire cloths were replaced by cloths or wires of synthetic fiber threads.
The advantage of synthetic threads beyond metal-wire threads primarily resides in their improved fatigue and wear resistance. Synthetic wires or papermaking fabrics do, however, suffer from the disadvantage of having considerably less stability than paper forming cloths made from metal-wires of corresponding coarseness.
Furthermore, with such papermaking fabrics formed of synthetic polymer materials it is desirable to provide the surfaces of the fabric with special properties to prevent the adhesion to the fabric of suspended particles present in the paper stock which would thereby reduce the drainage properties of the fabric. Adhering of such particles is an acute problem in the case where the liquid suspension, or pulp, used to make the paper contains suspended particles of filler clay, pitch (fatty acids) and/or polymer materials from repulped, deinked paper, in addition to suspended cellulose fibers. For example, a non-treated fabric installed on a corrugating machine could lose as much as 20% permeability during its useful life due to particle retention on the fabric. Similarly, there is the problem of adhesion from contaminants present in recycled paper, e.g. glue from envelopes.
In addition, with such papermaking fabrics it is desirable to provide the above mentioned special surface properties which are permanent and remain in place when the fabric has run for a few cycles on the papermaking machine. In the past, all fabrics treated to prevent adhesion lose the special surface properties from the treatment after a few cycles and therefore the problems associated with contamination from the sources described above remain a major concern in the papermaking industry.